The present invention relates to an electric automobile using a battery as a power source.
In recent years, there has been development of the electric automobile that attempt to achieve less environmental pollution without using petroleum fuel. The automobile has a battery that can be recharged by an engine generator. And the automobile runs by an electric motor that uses the battery as the power source. Thus, the electric automobile has a battery and a generator. As a result, weight and space are taken up by an engine that drives the generator.
In order to solve this problem, Japanese Patent Application Laid Open Number 1980-157901 discloses an electric automobile having an engine generator that automatically operates in accordance with the conditions of the battery, and the traveling or stopping condition of the electric vehicle.
In this prior art, the battery is charged when the gravity of the battery liquid becomes lower than a predetermined value or when the vehicle stops. And then, recharging is stopped when the gravity of the battery liquid rises to the predetermined value or when the vehicle travels. Therefore, the space and the weight taken by both the battery and the engine generator become more compact, so that the vehicle becomes lighter and thus performance is improved.
However, a ratio of operating time of the engine generator to traveling time of the vehicle, i.e., an assist ratio must be determined in accordance with the performance of the vehicle, mileage travel distance, the space taken by the engine (the engine weight), battery life, cost, appropriateness with respect to the environment, mental condition of a driver and/or other associated factors. Therefore, battery recharging is needed frequently when the battery is designed smaller and lighter than usual only in consideration of the battery charging condition. In addition such problems as shortened battery life, noise increasing and environmental pollution due to exhaust gas emissions.